This invention is based in part on the elucidation of new structural conformations and functions of the sodium/potassium adenosine triphosphate synthase (Na/K ATPase), and especially elucidation of new binding sites and interactions. The present invention provides applications of surprising structural and functional relationships between Na/K ATPase and compounds which interact with Na/K ATPase. The invention provides solutions to chemically affecting not only the Na/K ATPase interactions, but also regulators known to be upstream and downstream.
The Na/K-ATPase was originally discovered as an active ion transporter residing in the plasma membrane. The functional Na/K-ATPase is mainly consisted of α and β subunits. The a subunit is the catalytic subunit for it contains both ligand and nucleotide binding sites. Despite of its long reputation as an ion transporter, recent studies have revealed that the Na/K-ATPase, in addition to its ion pumping function, is capable of performing various other functions. For example, it was discovered that the Na/K-ATPase interacted with the Src kinase forming a functional signaling complex capable of transducing extracellular signals into activation of intracellular kinase cascades. Interestingly, the signaling Na/K-ATPase was demonstrated to mainly localize in the specialized plasma membrane microdomains called caveolae (“little caves”) and interact with caveolae marker, caveolin-1 protein. The caveolin-1 protein is an ˜22-kD protein mainly localized in the plasma membrane. In addition to its role in biogenesis of caveolae, it is known to play a role in cellular cholesterol homeostasis. It has been demonstrated to bind to cholesterol in a 1:1 ratio and involved in the trafficking of cholesterol between the plasma membrane and intracellular organelles. Furthermore, depletion of cellular cholesterol leads to redistribution of caveolin-1 to perinuclear regions. On the other hand, the Na/K-ATPase regulated the membrane trafficking of caveolin-1. Graded knockdown of the Na/K-ATPase α1 led to mobilization of caveolin-1 within caveolae domain and redistribution of caveolin-1 to perinuclear regions. Depletion of cellular cholesterol redistributed the Na/K-ATPase α1 out of caveolae.